Re: test_fsync label adjustments

On Jan 18, 2011, at 3:55 PM, Bruce Momjian wrote:

> I have modified test_fsync to use test labels that match wal_sync_method
> values, and and added more tests for open_sync with different sizes. 
> This should make the program easier for novices to understand.  Here is
> a test run for Ubuntu 11.04:
> 
> 	$ ./test_fsync
> 	2000 operations per test
> 	
> 	Compare file sync methods using one 8k write:
> 	(in wal_sync_method preference order, except fdatasync
> 	is Linux's default)
> 	        open_datasync (non-direct I/O)*    85.127 ops/sec
> 	        open_datasync (direct I/O)         87.119 ops/sec
> 	        fdatasync                          81.006 ops/sec
> 	        fsync                              82.621 ops/sec
> 	        fsync_writethrough                            n/a
> 	        open_sync (non-direct I/O)*        84.412 ops/sec
> 	        open_sync (direct I/O)             91.006 ops/sec
> 	* This non-direct I/O mode is not used by Postgres.

I am curious how this is targeted at novices. A naive user might enable the "fastest" option which could be exactly wrong. For this to be useful to novices, I suspect the tool will need to generate platform-specific suggestions, no?

Cheers,
M